Interference aware vertical handoff decision algorithm for quality of service support in wireless heterogeneous networks Celal Çeken a, * , Serhan Yarkan b , Hüseyin Arslan b a University of Kocaeli, Technical Education Faculty, Electronics and Computer Education Department, 41380 Kocaeli, Turkey b Department of Electrical Engineering, University of South Florida, 4202 E. Fowler Avenue, ENB–118, Tampa, FL 33620, United States article info Article history: Received 9 January 2009 Received in revised form 8 September 2009 Accepted 25 September 2009 Available online 12 October 2009 Responsible Editor: Ing. W. Kellerer Keywords: Vertical handoff Heterogeneous networks Decision making Fuzzy logic Interference abstract Next generation wireless networks concept aims at collaboration of various radio access technologies in order to provide quality of service (QoS) supported and cost efficient con- nections at anywhere and anytime. Since the next generation wireless systems are expected to be of heterogeneous topology, traditional handoff (horizontal handoff/hand- over) mechanisms are not sufficient to meet the requirements of these types of networks. More intelligent vertical handoff algorithms which consider user profiles, application requirements, and network conditions must be employed in order to provide enhanced performance results for both user and network. Moreover, frequency reuse of one (FRO) seems to be the strongest candidate of deployment options for next generation wireless networks; therefore, interference conditions gains a significant attention in vertical hand- off decision making process. In this study, a fuzzy logic-based handoff decision algorithm is introduced for wireless heterogeneous networks. The parameters; data rate, received sig- nal strength indicator (RSSI), and mobile speed are considered as inputs of the proposed fuzzy-based system in order to decide handoff initialization process and select the best candidate access point around a smart mobile terminal. Also, in contrast to the traditional fuzzy-based algorithms, the method proposed takes ambient interference power, which is referred to as interference rate, as another input to the decision process. The results show that the performance is significantly enhanced for both user and network by the method proposed. Ó 2009 Elsevier B.V. All rights reserved. 1. Introduction As wireless communication evolves, many different sig- naling schemes and methods emerge and are standardized. Despite the obvious dominance of some specific types of networks in daily life such as cellular mobile networks, emergence of new standards forces different types of net- works to coexist. Therefore, the concept ‘‘next generation networks” needs to allow for heterogeneous structure and to aim at collaboration of these various wireless tech- nologies in order to provide quality of service (QoS) supported and cost efficient connections at anywhere and anytime. Even though heterogeneous network structure is a very big concern by itself, terminals within the networks bring about some other issues for the next generation wireless networks. In this regard, it can be said that the next gener- ation wireless networks need to include terminals that are able to: (i) be aware of the existence of heterogeneous net- works around, and (ii) manage seamless transitions be- tween existing networks when necessary. Considering (i) and (ii) together, one can deduce that recently emerging technology called cognitive radio (CR) can be a remedy for both, since CRs are able to be aware of, learn about, and adapt to the changing conditions in radio environment 1389-1286/$ - see front matter Ó 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.comnet.2009.09.018 * Corresponding author. Tel.: +90 2623032240. E-mail addresses: cceken@kocaeli.edu.tr (C. Çeken), syarkan@mail. usf.edu (S. Yarkan), arslan@eng.usf.edu (H. Arslan). Computer Networks 54 (2010) 726–740 Contents lists available at ScienceDirect Computer Networks journal homepage: www.elsevier.com/locate/comnet